Improvement in door-locks



W.P.DODSON.

Improvementin Door Lock&

No.\24,42. ,y FTE l Patengdmawhlmsvz.`

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UNITED STATES PATENT OFFICE.

IMPROVEMENT IN Doon-Locks.

Specication forming part of Letters Patent No. 124,424, dated March 12, 1872.

Specification describing a certain Improvement in Locks, invented by VILsoN P. DoD- SON, of the city and county of Philadelphia and State of Pennsylvania.

My invention relates to an improvement in door-locks 5 and consists in arranging the working parts in such a manner that, when the key is placed in one hole and turned twice, it removes the bolt beyondl the reach of a key or instrument placed in the opposite key-hole, the object of which is to lock it upon the inside ot' a room to prevent its being tampered with or unlocked from the outside.

Figure l is a plan view of my improvement in door-locks. Fig. 2 is a plan of the same, showing the bolt partially projected from the casing, With a portion of it broken away. Fig 3 is also a plan, showing the bolt projected to its fullest extent, when the door is locked on the inside. The bolt is shown with a portion of it broken away. Fig. 4 is a view ofthe reverse side of the bolt detached from the casing.

The casing A ot' the lock is made in the ordinary form, and is provided in the interior with a bolt, B, one end of which is supported on a shoulder, C, formed in the casing, and the opposite extremity passes through a suitable slot in the end ofthe lock. The bolt B is provided on its lower edge with three notches, D, D1, and D2. The notch D2 is made at one end, and the adjacent notches D and D1 at about the middle ot' its length. These notches are formed for the reception of the bit of the key. The casing A is provided on its opposite`sides with two key-holes, e and e', which are located at a certain distance apart. The hole e, which is intended for the inside of the door, is made close to the adjacent notches D .and D1 in the bolt, so that when the key is introduced and turned twice, the bit of it will come alternately in contact with them. The hole e is made in the cover-plate E, which incloses the casin g, and is intended to receive the key from the outside of the door. The bit in this case operates in the notch D2 at the end of the bolt. The metal forming the shoulder C in the casing is of considerable width, and has formed in it a socket,

F, in which the end of the key rotates, and a portion of it also projects out at right angles, as shown at G in the drawing, and is ot the same height as the bolt, thus forming a guard to prevent the withdrawal of the bolt by a key or instrument. In order toprevent the bolt being forced back by any instrument, it is provided on its lower edge with recesses 7L and h, the shoulders of which are brought in contact (when the bolt is actuated) with a lug, I, formed in the casing. The spring J, which bears on the upper edge of the bolt, presses it down to its bearings 5' and it is also of proper elasticity to permit it to rise sufficiently, when the key is applied, to clear the lug I.

In opera-ting the lock, if the keyis placed in the key-hole e on the inside of the door and turned twice, the bolt will assume the position as shown in Fig. S-that is, projected to its full. extent. In this position it will be impossible to unlock it from the outside of the room, as the notch D2 has passed beyond the reach of the bit of the key, and the guard G prevents its being tampered with by a key of a different form, or any instrument. If the key is turned but once on theY inside, -the lock may be readily opened from the outside by a similar key.

I claim as my invention- The combination ofthe bolt B, provided wi th the notches D, D1, and D2 and recesses h and h', casing A, lug I, shoulder O, spring J, guard G, and key-holes e and e', when the key at e, by its second throw, removes the bolt beyond the reach of the key at c', substantially in the manner and for the purpose herein shown and described.

' WILSON vP. DODSON.

Witnesses:

IsAAc It.l OAKFORD, FRANK SroU'r. 

